package l.l.w.practice.EqualDifferenceSeries;

import java.util.Scanner;

/**
 * Created by llw on 2017/10/8.
 */
public class EqualDifferenceSeries {

    public boolean isEqualDifferenceSeries(int[] nums){
        int min = Integer.MAX_VALUE;
        int sum = 0;
        int n = nums.length;
        for(int i = 0; i < n; ++i){
            int num = nums[i];
            if(num < min){
                min = num;
            }
            sum += num;
        }
        if((sum - n*min)%(n*(n-1)/2)==0) return true;
        return false;
    }
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] nums = new int[n];
        for(int i = 0 ; i < n; ++i){
            nums[i] = scanner.nextInt();
        }
        boolean result = new EqualDifferenceSeries().isEqualDifferenceSeries(nums);
        if(result) System.out.println("Possible");
        else System.out.println("Impossible");
    }
}
